Material for the controlled vaporization of a liquid cryogen

Abstract

A shaped article is capable of at least one of containing and delivering a cryogenic fluid. The article has a porous structure that restricts the passage of cryogenic fluid in the liquid phase while permitting the passage of cryogenic fluid in the gaseous phase. The article may be in the form of a tube or container. The article permits a liquid cryogen to be transported to a specific site, and then cool the site by means of conduction from the cold article and convection of cold gas, the phase change of the evaporating liquid greatly enhancing the heat loss.

What is claimed is:  
     
       1. A shaped article comprising fluoropolymer having a porous structure and a liquid nitrogen leak pressure of at least 0.002 MPa and which restricts the passage of cryogenic fluid in the liquid phase while permitting the passage of cryogenic fluid in the gaseous phase. 
     
     
       2. The article of  claim 1  that is flexible below 0° Celsius. 
     
     
       3. The article of  claim 2 , wherein said article is flexible at cryogenic temperatures. 
     
     
       4. The article of  claim 3 , wherein said article is flexible at about 77 Kelvin. 
     
     
       5. The shaped article of  claim 1  in the form of a tube. 
     
     
       6. The tube of  claim 5  wherein the fluoropolymer is PTFE. 
     
     
       7. The tube of  claim 6  wherein the fluoropolymer is ePTFE. 
     
     
       8. The tube of  claim 6  in which said tube comprises multiple layers of PTFE film. 
     
     
       9. The tube of  claim 8  wherein the PTFE film comprises expanded PTFE. 
     
     
       10. The tube of  claim 5  further including external reinforcement. 
     
     
       11. The tube of  claim 5  that is flexible below 0° Celsius. 
     
     
       12. The tube of  claim 5  in which said tube comprises PTFE and at least one other fluoropolymer. 
     
     
       13. The tube of  claim 5  in which said tube comprises PTFE and at least one other polymer. 
     
     
       14. The tube of  claim 13  in which the other polymer is a copolymer of tetrafluoroethylene and hexafluoropropylene. 
     
     
       15. The tube of  claim 13  in which the other polymer is a copolymer of tetrafluoroethylene and perfluropropylvinyl ether. 
     
     
       16. The tube of  claim 5  in which said tube comprises part of a medical device. 
     
     
       17. The article of  claim 1  wherein the article comprises a material that has a thermal conductivity of about 0.23 Watts/m K or lower. 
     
     
       18. The shaped article of  claim 1  wherein said article has a liquid nitrogen leak pressure (LNLP) of greater than or equal to about 0.003 MPa. 
     
     
       19. The shaped article of  claim 18  wherein said article has a LNLP between 0.003 and 0.075 MPa. 
     
     
       20. The shaped article of  claim 19  wherein said article has an LNLP between 0.04 and 0.06 MPa.